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Purpose: The risk of exercise-induced endotoxemia is increased in the heat and is primarily attributable to changes in gut permeability resulting in the translocation of lipopolysaccharides (LPS) into the circulation. The purpose of this study was to quantify the acute changes in gut permeability and LPS translocation during submaximal continuous and high-intensity interval exercise under heat stress. Methods: A total of 12 well-trained male runners (age 37 [7] y, maximal oxygen uptake [VO2max] 61.0 [6.8] mL·min−1·kg−1) undertook 2 treadmill runs of 2 × 15-minutes at 60% and 75% VO2max and up to 8 × 1-minutes at 95% VO2max in HOT (34°C, 68% relative humidity) and COOL (18°C, 57% relative humidity) conditions. Venous blood samples were collected at the baseline, following each running intensity, and 1 hour postexercise. Blood samples were analyzed for markers of intestinal permeability (LPS, LPS binding protein, and intestinal fatty acid–binding protein). Results: The increase in LPS binding protein following each exercise intensity in the HOT condition was 4% (5.3 μg·mL−1, 2.4–8.4; mean, 95% confidence interval, P <.001), 32% (4.6 μg·mL−1, 1.8–7.4; P =.002), and 30% (3.0 μg·mL−1, 0.03–5.9; P =.047) greater than in the COOL condition. LPS was 69% higher than baseline following running at 75% VO2max in the HOT condition (0.2 endotoxin units·mL−1, 0.1–0.4; P =.011). Intestinal fatty acid–binding protein increased 43% (2.1 ng·mL−1, 0.1–4.2; P =.04) 1 hour postexercise in HOT compared with the COOL condition. Conclusions: Small increases in LPS concentration during exercise in the heat and subsequent increases in intestinal fatty acid–binding protein and LPS binding protein indicate a capacity to tolerate acute, transient intestinal disturbance in well-trained endurance runners. [ABSTRACT FROM AUTHOR]

Purpose: To quantify, for an elite-level racewalker, altitude training, heat acclimation and acclimatization, physiological data, and race performance from January 2007 to August 2008. Methods: The participant performed 7 blocks of altitude training: 2 "live high:train high" blocks at 1380 m (total = 22 d) and 5 simulated "live high:train low" blocks at 3000 m/600 m (total = 98 d). Prior to the 2007 World Championships and the 2008 Olympic Games, 2 heat-acclimation blocks of ~6 weeks were performed (1 session/week), with ∼2 weeks of heat acclimatization completed immediately prior to each 20-km event. Results: During the observation period, physiological testing included maximal oxygen uptake (VO2max, mL·kg−1·min−1), walking speed (km·h−1) at 4 mmol·L−1 blood lactate concentration [La−], body mass (kg), and hemoglobin mass (g), and 12 × 20-km races and 2 × 50-km races were performed. The highest VO2max was 67.0 mL·kg−1·min−1 (August 2007), which improved 3.1% from the first measurement (64.9 mL·kg−1·min−1, June 2007). The highest percentage change in any physiological variable was 7.1%, for 4 mmol·L−1 [La−] walking speed, improving from 14.1 (June 2007) to 15.1 km·h−1 (August 2007). Personal-best times for 20 km improved from (hh:mm:ss) 1:21:36 to 1:19:41 (2.4%) and from 3:55:08 to 3:39:27 (7.1%) in the 50-km event. The participant won Olympic bronze and silver medals in the 20- and 50-km, respectively. Conclusions: Elite racewalkers who regularly perform altitude training may benefit from periodized heat acclimation and acclimatization prior to major international competitions in the heat. [ABSTRACT FROM AUTHOR]

Purpose: Critical speed (CS) and supra-CS distance capacity (D') are useful metrics for monitoring changes in swimmers' physiological and performance capacities. However, the utility of these metrics across a season has not been systematically evaluated in high-level swimmers. Methods: A total of 27 swimmers (mean [SD]: 18 females, age= 19.1 [2.9] y, and 9 males, age = 19.5 [1.9] y) completed the 12 x 25-m swimming test multiple times (4 [3] tests/swimmer) across a 2-y period. Season-best times in all distances for the test stroke were sourced from publicly available databases. Swimmers' distance speciality was determined as the event with the time closest to world record. Four metrics were calculated from the 12 x 25-m lest: CS, D', peak speed, and drop-off %. Results: Guyatt responsiveness index values were calculated to ascertain the practically relevant sensitivity of each 12 x 25-m metric: CS = 1.5, peak speed = 2.3, D' = 2.1, and drop-off % = 2.6. These values are modified effect sizes; all are large effects. Bayesian mixed modeling showed substantial between-subjects differences between genders and strokes for each variable but minimal within-subject changes across the season. Drop-off % was lower in 200-m swimmers (14.0% [3.3%]) than in 100-m swimmers (18.1% [4.1%], P - .003, effect size = 1.10). Conclusions: The 12x25-m test is best suited to differentiating between swimmers ol different strokes and events. Further development is needed to improve its utility in quantifying meaningful changes over a season for individual swimmers. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether combining training in heat with "Live High, Train Low" hypoxia (LHTL) further improves thermoregulatory and cardiovascular responses to a heat-tolerance test compared with independent heat training. Methods: A total of 25 trained runners (peak oxygen uptake = 64.1 [8.0] mL·min−1·kg−1) completed 3-wk training in 1 of 3 conditions: (1) heat training combined with "LHTL" hypoxia (H+H; FiO2 = 14.4% [3000 m], 13 h·d−1; train at <600 m, 33°C, 55% relative humidity [RH]), (2) heat training (HOT; live and train <600 m, 33°C, 55% RH), and (3) temperate training (CONT; live and train <600 m, 13°C, 55% RH). Heat adaptations were determined from a 45-min heat-response test (33°C, 55% RH, 65% velocity corresponding to the peak oxygen uptake) at baseline and immediately and 1 and 3 wk postexposure (baseline, post, 1 wkP, and 3 wkP, respectively). Core temperature, heart rate, sweat rate, sodium concentration, plasma volume, and perceptual responses were analyzed using magnitude-based inferences. Results: Submaximal heart rate (effect size [ES] = −0.60 [−0.89; −0.32]) and core temperature (ES = −0.55 [−0.99; −0.10]) were reduced in HOT until 1 wkP. Sweat rate (ES = 0.36 [0.12; 0.59]) and sweat sodium concentration (ES = −0.82 [−1.48; −0.16]) were, respectively, increased and decreased until 3 wkP in HOT. Submaximal heart rate (ES = −0.38 [−0.85; 0.08]) was likely reduced in H+H at 3 wkP, whereas CONT had unclear physiological changes. Perceived exertion and thermal sensation were reduced across all groups. Conclusions: Despite greater physiological stress from combined heat training and "LHTL" hypoxia, thermoregulatory adaptations are limited in comparison with independent heat training. The combined stimuli provide no additional physiological benefit during exercise in hot environments. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of natural altitude training (NAT) and simulated (SIM) live high:train low altitude training on road-race walking performance (min), as well as treadmill threshold walking speed (km·h−1) at 4 mmol·L−1 and maximal oxygen consumption, at 1380 m. Methods: Twenty-two elite-level male (n = 15) and female (n = 7) race walkers completed 14 d of NAT at 1380 m (n = 7), SIM live high:train low at 3000:600 m (n = 7), or control conditions (600-m altitude; CON, n = 8). All preintervention and postintervention testing procedures were conducted at 1380 m and consisted of an incremental treadmill test, completed prior to a 5 × 2-km road-race walking performance test. Differences between groups were analyzed via mixed-model analysis of variance and magnitude-based inferences, with a substantial change detected with >75% likelihood of exceeding the smallest worthwhile change. Results: The improvement in total performance time for the 5 × 2-km test in NAT was not substantially different from SIM but was substantially greater (85% likely) than CON. The improvement in percentage decrement in the 5 × 2-km performance test in NAT was greater than in both SIM (93% likely) and CON (93% likely). The increase in maximal oxygen consumption was substantially greater (91% likely) in NAT than in SIM. Improvement in threshold walking speed was substantially greater than CON for both SIM (91% likely) and NAT (90% likely). Conclusions: Both NAT and SIM may allow athletes to achieve reasonable acclimation prior to competition at low altitude. [ABSTRACT FROM AUTHOR]

High-level athletes are always looking at ways to maximize training adaptations for competition performance, and using altered environmental conditions to achieve this outcome has become increasingly popular by elite athletes. Furthermore, a series of potential nutrition and hydration interventions may also optimize the adaptation to altered environments. Altitude training was first used to prepare for competition at altitude, and it still is today; however, more often now, elite athletes embark on a series of altitude training camps to try to improve sea-level performance. Similarly, the use of heat acclimation/acclimatization to optimize performance in hot/humid environmental conditions is a common practice by high-level athletes and is well supported in the scientific literature. More recently, the use of heat training to improve exercise capacity in temperate environments has been investigated and appears to have positive outcomes. This consensus statement will detail the use of both heat and altitude training interventions to optimize performance capacities in elite athletes in both normal environmental conditions and extreme conditions (hot and/or high), with a focus on the importance of nutritional strategies required in these extreme environmental conditions to maximize adaptations conducive to competitive performance enhancement. [ABSTRACT FROM AUTHOR]

The International Association of Athletics Federations recognizes the importance of nutritional practices in optimizing an Athlete's well-being and performance. Although Athletics encompasses a diverse range of track-and-field events with different performance determinants, there are common goals around nutritional support for adaptation to training, optimal performance for key events, and reducing the risk of injury and illness. Periodized guidelines can be provided for the appropriate type, amount, and timing of intake of food and fluids to promote optimal health and performance across different scenarios of training and competition. Some Athletes are at risk of relative energy deficiency in sport arising from a mismatch between energy intake and exercise energy expenditure. Competition nutrition strategies may involve pre-event, within-event, and between-event eating to address requirements for carbohydrate and fluid replacement. Although a "food first" policy should underpin an Athlete's nutrition plan, there may be occasions for the judicious use of medical supplements to address nutrient deficiencies or sports foods that help the athlete to meet nutritional goals when it is impractical to eat food. Evidence-based supplements include caffeine, bicarbonate, beta-alanine, nitrate, and creatine; however, their value is specific to the characteristics of the event. Special considerations are needed for travel, challenging environments (e.g., heat and altitude); special populations (e.g., females, young and masters athletes); and restricted dietary choice (e.g., vegetarian). Ideally, each Athlete should develop a personalized, periodized, and practical nutrition plan via collaboration with their coach and accredited sports nutrition experts, to optimize their performance. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effect of altitude training at 1600 and 1800 m on sea-level (SL) performance in national-level runners. Methods: After 3 wk of SL training, 24 runners completed a 3-wk sojourn at 1600 m (ALT1600, n = 8), 1800 m (ALT1800, n = 9), or SL (CON, n = 7), followed by up to 11 wk of SL racing. Race performance was measured at SL during the lead-in period and repeatedly postintervention. Training volume (in kilometers) and load (session rating of perceived exertion) were calculated for all sessions. Hemoglobin mass was measured via CO rebreathing. Between-groups differences were evaluated using effect sizes (Hedges g). Results: Performance improved in both ALT1600 (mean [SD] 1.5% [0.9%]) and ALT1800 (1.6% [1.3%]) compared with CON (0.4% [1.7%]); g = 0.83 (90% confidence limits −0.10, 1.66) and 0.81 (−0.09, 1.62), respectively. Season-best performances occurred 5 to 71 d postaltitude in ALT1600/1800. There were large increases in training load from lead-in to intervention in ALT1600 (48% [32%]) and ALT1800 (60% [31%]) compared with CON (18% [20%]); g = 1.24 (0.24, 2.08) and 1.69 (0.65, 2.55), respectively. Hemoglobin mass increased in ALT1600 and ALT1800 (∼4%) but not CON. Conclusions: Larger improvements in performance after altitude training may be due to the greater overall load of training in hypoxia compared with normoxia, combined with a hypoxia-mediated increase in hemoglobin mass. A wide time frame for peak performances suggests that the optimal window to race postaltitude is individual, and factors other than altitude exposure per se may be important. [ABSTRACT FROM AUTHOR]

To validate [[??]o.sub.2] and energy expenditure predictions by the Suunto heart rate (HR) system against a first principle gas analysis system, well-trained male (n = 10, age 29.8 [+ or -] 4.3 years, [[??]o.sub.2] 65.9 [+ or -] 9.7 ml x [kg.sup.-1] x [min.sup.-1]) and female (n= 7, 25.6 [+ or -] 3.6 years, 57.0 [+ or -] 4.2 ml x [kg.sup.-1] x [min.sup.-1]) runners completed a 2-stage incremental running test to establish submaximal and maximal oxygen uptake values. Metabolic cart values were used as the criterion measure of [[??]o.sub.2] and energy expenditure (kJ) and compared with the predicted values from the Suunto software. The 3 levels of software analysis for the Suunto system were basic personal information (BI), BI + measured maximal HR ([BI.sub.hr]), and [BI.sub.hr] + measured [[??]o.sub.2] ([BI.sub.hr + v]). Comparisons were analyzed using linear regression to determine the standard error of the estimate (SEE). Eight subjects repeated the trial within 7 days to determine reliability (typical error [TE]). The SEEs for oxygen consumption via BI, [BI.sub.hr], and [BI.sub.hr + v] were 2.6, 2.8, and 2.6 ml x [kg.sup.-1] x [min.sup.-1], respectively, with corresponding percent coefficient of variation (%CV) of 6.0, 6.5, and 6.0. The bias compared with the criterion [[??]o.sub.2] decreased from -6.3 for BI, -2.5 for [BI.sub.hr], to 0.9% for [BI.sub.hr + v]. The SEE of energy expenditure improved from BI (6.74 kJ) to [BI.sub.hr] (6.56) and [BI.sub.hr + v] (6.14) with corresponding %CV of 13.6, 12.2, and 12.7. The TE values for [[??]o.sub.2] were ~0.60 ml x [kg.sup.-1] x [min.sup.-1] and ~2 kJ for energy expenditure. The %CV for [??]o2 and energy expenditure was ~1 to 4%. Although reliable, basic HR-based estimations of [[??]o.sub.2] and energy expenditure from the Suunto system underestimated [[??]o.sub.2] and energy expenditure by ~6 and 13%, respectively. However, estimation can be improved when maximal HR and [[??]o.sub.2] values are added to the software analysis. KEY WORDS aerobic capacity, intermittent exercise, team sport

Repeated sprint testing is gaining popularity in team sports, but the methods of data analysis and relationships to speed and endurance qualities are not well described. We compared three different methods for analyzing repeated sprint test results, and we quantified relationships between repeated sprints, short sprints, and endurance test scores. Well-trained male junior Australian Football players (n = 60, age 18.1 [+ or -] 0.4 years, height 1.88 [+ or -] 0.07 m, mass 82.0 [+ or -] 8.1 kg; mean [+ or -] SD) completed a 6 x 30-m repeated sprint running test on a 20-second cycle, a 20-m sprint test (short sprint), and the 20-m multistage shuttle run for endurance. Repeated sprint results were evaluated in three ways: total time for all six sprints (TOTAL), percent change from predicted times (PRED) from the fastest 30-m sprint time, and percent change from first to last sprint (CHANGE). We observed a very large decrement (CHANGE 6.3 [+ or -] 0.7%, mean [+ or -] 90% confidence limits) in 30-m performance from the first to last sprint (4.16 [+ or -] 0.10 to 4.42 [+ or -] 0.11 seconds, mean [+ or -] SD). Results from TOTAL were highly correlated with 20-m sprint and 20-m multistage shuttle run tests. Performance decrements calculated by PRED were highly correlated with TOTAL (r = 0.91), but neither method was directly comparable with CHANGE (r = -0.23 and r = 0.12 respectively). TOTAL was moderately correlated with fastest 20m sprint time (r = 0.66) but not the 20-m multistage shuttle run (r = -0.20). Evaluation of repeated sprint testing is sensitive to the method of data analysis employed. The total sprint time and indices of the relative decrement in performance are not directly interchangeable. Repeated sprint ability seems more related to short sprint qualities than endurance fitness.

Fifteen highly trained distance runners ([Vo.sub.2]max 71.1 [+ or -] 6.0 ml x [min.sup.-1] x [kg.sup.-1], mean [+ or -] SD) were randomly assigned to a plyometric training (PLY; n = 7) or control (CON; n = 8) group. In addition to their normal training, the PLY group undertook 3 X 30 minutes PLY sessions per week for 9 weeks. Running economy (RE) was assessed during 3 X 4 minute treadmill runs (14, 16, and 18 km x [h.sup.-1]), followed by an incremental test to measure [Vo.sub.2]max. Muscle power characteristics were assessed on a portable, unidirectional ground reaction force plate. Compared with CON, PLY improved RE at 18 [km x [h.sup.-1] (4.1%, p = 0.02), but not at 14 or 16 km.[h.sup.-1]. This was accompanied by trends for increased average power during a 5-jump plyometric test (15%, p = 0.11), a shorter time to reach maximal dynamic strength during a strength quality assessment test (14%, p = 0.09), and a lower [Vo.sub.2]-speed slope (14%, p = 0.12) after 9 weeks of PLY. There were no significant differences in cardiorespiratory measures or [Vo.sub.2]max as a result of PLY. In a group of highly-trained distance runners, 9 weeks of PLY improved RE, with likely mechanisms residing in the muscle, or alternatively by improving running mechanics. KEY WORDS. oxygen consumption, strength training, elite runners

The aim of this study was to characterize relationships between anthropometric and isoinertial strength characteristics and bowling speed in junior and senior cricket fast bowlers. Subjects were first-class senior (n = 24; mean [+ or -] SD age = 23.9 [+ or -] 4.8 years, height = 187.4 [+ or -] 4.8 cm, mass = 87.8 [+ or -] 8.4 kg) and junior representative (n = 48; mean [+ or -] SD age = 14.8 [+ or -] 1.3 years, height = 175.7 [+ or -] 9.8 cm, mass = 65.8 [+ or -] 12.9 kg) male fast bowlers. A full anthropometric profile, upper- and lower-body isoinertial strength tests, and peak bowling speed (Vpeak) were assessed on the same day. The senior bowlers had a substantially faster Vpeak (126.7 km*[h.sup.-1]) than the juniors (99.6 km*[h.sup.-1]), a larger estimated muscle mass (seniors 40.0 [+ or -] 3.9 kg, juniors 28.3 [+ or -] 5.6 kg), and a greater bench press throw and deltoid throw (all p < 0.01). The best multiple predictors of Vpeak for the junior bowlers were the static jump, bench throw, body mass, percentage muscle mass, and height (multiple-correlation r = 0.86). For the senior bowlers, static jump and arm length correlated positively with Vpeak (multiple-correlation r = 0.74). The 1-legged countermovement jump was negatively correlated with Vpeak in both groups. We conclude that differences in Vpeak between junior and senior bowlers relate primarily to body mass and upper-body strength. However, lower body strength is a more important contributor to Vpeak in senior bowlers. Key Words. cricket, performance, isoinertial strength, anthropometry, ball-release speed, age

Purpose: To determine the effect of training at 2100-m natural altitude on running speed (RS) during training sessions over a range of intensities relevant to middle-distance running performance. Methods: In an observational study, 19 elite middle-distance runners (mean ± SD age 25 ± 5 y, VO2max, 71 ± 5 mL ⋅ kg-1 ⋅ min-1) completed either 4-6 wk of sea-level training (CON, n = 7) or a 4- to 5-wk natural altitude-training camp living at 2100 m and training at 1400-2700 m (ALT, n = 12) after a period of sea-level training. Each training session was recorded on a GPS watch, and athletes also provided a score for session rating of perceived exertion (sRPE). Training sessions were grouped according to duration and intensity. RS (km/h) and sRPE from matched training sessions completed at sea level and 2100 m were compared within ALT, with sessions completed at sea level in CON describing normal variation. Results: In ALT, RS was reduced at altitude compared with sea level, with the greatest decrements observed during threshold- and VO2 max-intensity sessions (5.8% and 3.6%, respectively). Velocity of low-intensity and race-pace sessions completed at a lower altitude (1400 m) and/or with additional recovery was maintained in ALT, though at a significantly greater sRPE (P = .04 and .05, respectively). There was no change in velocity or sRPE at any intensity in CON. Conclusion: RS in elite middle-distance athletes is adversely affected at 2100-m natural altitude, with levels of impairment dependent on the intensity of training. Maintenance of RS at certain intensities while training at altitude can result in a higher perceived exertion. [ABSTRACT FROM AUTHOR]

High altitude exposure can increase resting metabolic rate (RMR) and induce weight loss in obese populations, but there is a lack of research regarding RMR in athletes at moderate elevations common to endurance training camps. The present study aimed to determine whether 4 weeks of classical altitude training affects RMR in middle-distance runners. Ten highly trained athletes were recruited for 4 weeks of endurance training undertaking identical programs at either 2200m in Flagstaff, Arizona (ALT, n = 5) or 600m in Canberra, Australia (CON, n = 5). RMR, anthropometry, energy intake, and hemoglobin mass (Hbmass) were assessed pre- and posttraining. Weekly run distance during the training block was: ALT 96.8 ± 18.3km; CON 103.1 ± 5.6km. A significant interaction for Time*Group was observed for absolute (kJ.day-1) (F-statistic, p-value: F(1,8)=13.890, p = .01) and relative RMR (F(1,8)=653.453, p = .003) POST-training. No significant changes in anthropometry were observed in either group. Energy intake was unchanged (mean ± SD of difference, ALT: 195 ± 3921kJ, p = .25; CON: 836 ± 7535kJ, p = .75). A significant main effect for time was demonstrated for total Hbmass (g) (F(1,8)=13.380, p = .01), but no significant interactions were observed for either variable [Total Hbmass (g): F(1,8)=1.706, p = .23; Relative Hbmass (g⋅kg-1): F(1,8)=0.609, p = .46]. These novel findings have important practical application to endurance athletes routinely training at moderate altitude, and those seeking to optimize energy management without compromising training adaptation. Altitude exposure may increase RMR and enhance training adaptation,. During training camps at moderate altitude, an increased energy intake is likely required to support an increased RMR and provide sufficient energy for training and performance. [ABSTRACT FROM AUTHOR]

It is unclear whether physiological measures monitored in an incremental treadmill test during a training season provide useful diagnostic information about changes in distance running performance. Purpose: To quantify the relationship between changes in physiological measures and performance (peak running speed) over a training season. Methods: Well-trained distance runners (34 males; VO2max 64 ± 6 mL·kg-1·min-1, mean ± SD) completed four incremental treadmill tests over 17 wk. The tests provided values of peak running speed, VO2max, running economy, and lactate threshold (as speed and %VO2max). The physiological measures were included in simple and multiple linear regression models to quantify the relationship between changes in these measures and changes in peak speed. Results: The typical within-subject variation in peak speed from test to test was 2.5%, whereas those for physiological measures were VO2max (mL·min-1·kg-1) 3.0%, economy (m·kg·mL-1) 3.6%, lactate threshold (%VO2max) 8.7%, and body mass 1.8%. In simple models these typical changes predicted the following changes in performance: VO2max 1.4%, economy 0.8%, lactate threshold -0.3%, and body mass -0.2% (90% confidence limits ∼±0.7%); the corresponding correlations with performance were 0.57, 0.33, -0.05, and -0.13 respectively (∼±0.20). In a multiple linear regression model, the contribution of each physiological variable to performance changed little after adjustment for the other variables. Conclusion: Change in VO2max in an incremental test during a running season is a good predictor of change in peak running speed, change in running economy is a moderate predictor, and lactate threshold and body mass provide little additional information. [ABSTRACT FROM AUTHOR]

We quantified the effect of an extended live high-train low (LHTL) simulated altitude exposure followed by a series of training camps at natural moderate altitude on competitive performance in seven elite middle-distance runners (Vo2max 71.4 ± 3.4 mL·min-1·kg-1, mean ± SD). Runners spent 44 ± 7 nights (mean ± SD) at a simulated altitude of 2846 ± 32 m, and a further 4 × 7- to 10-d training at natural moderate altitude (1700-2200 m) before racing. The combination of simulated LHTL and natural altitude training improved competitive performance by 1.9% (90% confidence limits, 1.3-2.5%). Middle-distance runners can confidently use a combination of simulated and natural altitude to stimulate adaptations responsible for improving performance. [ABSTRACT FROM AUTHOR]

Eighteen highly-trained runners ran two half marathons in mild environmental conditions, 3 wk apart, consuming either 426 ± 227 mL of a flavored placebo drink (PLACEBO) or an equivalent volume of water (386 ± 185 mL) and a commercial gel (GEL) supplying 1.1 ± 0.2 g/kg body mass (BM) carbohydrate (CHO). Voluntary consumption of this fluid was associated with a mean BM change of ∼ 2.4%. Runners performed better in their second race by 0.9% or 40 s (P = 0.03). Three runners complained of gastrointestinal discomfort in GEL trial, which produced a clear impairment of half-marathon performance by 2.4% or 105 s (P = 0.03). The effect of GEL on performance was trivial: time was improved by 0.3% or 14 s compared with PLACEBO (P = 0.52). Consuming the gel was associated with a 2.4% slower time through the 2 × 200 m feed zone; adding a trivial ∼ 2 s to race time. Although benefits to half marathon performance were not detected, the theoretical improvement during 1-h exercise with CHO intake merits further investigation. [ABSTRACT FROM AUTHOR]